• Journal of the Korean Geophysical Society
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• v.3 no.4
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• pp.281-290
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• 2000

This research was carried out in order to give some reasonable solutions on basin tectonics and on continental geodynamics, which are approached by using integrative researches on crustal deformation, 3-D seismic velocity reconstruction and geochemical tracing of volcanic rocks in the eastern China basin system.

• Journal of the Speleological Society of Korea
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• no.79
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• pp.31-39
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• 2007

대금굴은 3년여 동안 암석 틈새를 들춰내며 150m쯤 물길을 찾아 들어가, 다시 18m의 수직동굴로 하강하여 좁은 틈새를 비집고 70m를 들어가는 악전고투의 탐사 끝에 2003년 동굴을 발견했다. 이렇게 3년여 동안 발굴된 대금굴은 또다시 4년여 동안의 모노레일 설치와 동굴내부 관람로 및 조명설치 등의 공사를 거쳐 2097년 6월 5일 일반 공개를 하였다. 총 길이 610m 중 4분의 3정도는 동굴 입구로 향하는 산길이고 나머지는 동굴 안쪽 길이다. 승강장에서 동굴 내부 140m에 설치된 "대금역"까지는 약 7분이 걸린다. 운전석이 없고 자동으로 운행하기 때문에 앞뒤로 동굴 안팎이 잘 보인다. 동굴 내부에 열차를 타고 들어가는 건 분명 이색체험이다. 그러나 모노레일 내부에 울리는 비발디의 "사계"라든지 동굴 벽에 붙여 놓은, 네온 빛에 가까운 퍼런 빛깔의 조명이 조용한 동굴 감상에 역효과가 초래될 수도 있다.

• Economic and Environmental Geology
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• v.45 no.6
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• pp.599-622
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• 2012

The phase I soil geochemical exploration was carried out targeting around Chau Binh area far from about 14 km with southeastern direction from Quy Chau within Nghe An province. The interval of sampling are horizontal 300 m with 14 line and longitudinal 500 m with 15 line, resulting in 194 soil samples. Based on the result of the phase I soil geochemical exploration, the phase II detailed pitting survey was carried out targeting the grid point with high TREO content, resulting in 56 soil samples within 7 pits. The geology of survey area are consisted of Ban Chieng biotite granite complex and Dai Loc gneissic granite complex intruding Bu Khang formation comprising of schist, gneiss and limestone. Main mineralization in the study area have the characteristics of occurrence with tin, ruby and REE-bearing monazite(about 300 g/t) and xenotime(about 10 g/t) to be thought as occurring at the alteration zone of granite complex. In order to elucidate the source rock of monazite and xenotime confirmed from heavy sand, soil geochemical exploration was carried out. As a analysis result with ICP-MS on the soil samples from the phase I soil geochemical exploration, total REE oxide content of background amount to about 2 times of crustal abundance, enriching the heavy rare earth(about 2 times) and light rare earth(about 1.84 times). As a analysis result with ICP-MS on the soil samples from the phase II soil detailed pit survey, we identified outcrop considering as economic ore body at the grid point 4-7 pit with N40W attitude. As a synthetic consideration on the phase I soil geochemical exploration and phase II detailed pit survey, we tentatively designated areas considering as the extension of economic ore body with REE anomaly. In the near future, we have the plan to carry out the geophysical exploration and test drilling targeting the interval anticipated to the economic ore body.

• Journal of the Korean Geophysical Society
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• v.5 no.4
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• pp.283-292
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• 2002

The Korean peninsula is located at the edge of the East Asian active margin. The seismic activity in the Korean Peninsula is relatively low compared with the neighboring countries China and Japan. According to the available Seismic information, the Korean Peninsula is not totally safe from the Earthquake disaster. Moreover, the area is surrounded by varies tectonic forces which is resulted from the relative movements of the surrounding tectonic plates "Pacific, Philippine Sea, Eurasian and South China". Nowadays South Korea has 65 GPS stations belong to 5 governmental organizations "each organization figure out its own GPS stations for different requirements" In order to minimize the seismic hazard in the Korean Peninsula a program for monitoring the recent crustal movement has been designed considering the uses of the available GPS station "some selected stations from the previously mentioned stations" and the tectonic settings in and around the Korean Peninsula. This program is composed of two main parts, the first part to monitor the crustal deformation around the Korean Peninsula with the collaboration of the surrounding countries "China and Japan" this part is composed of two phases "East Sea Phase and Yellow Sea Phase". These phases will be helpful in determining the deformation parameters in the East Sea and the Yellow Sea respectively While the Second part of this program, is designed to determine the deformation parameters id and around the main faults in the Korean Peninsula and the relative movement between the Korean Peninsula and the Cheju Island. Through out this study the needs of crustal movement center rose up to collect the data from the previously mentioned stations and Organizations in order to use such reliable data in different geodynamical application.

• Tunnel and Underground Space
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• v.13 no.3
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• pp.187-195
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• 2003

This case study which is to make 2-Dimension earth's crust structures clearly is about the great boring-hole blasting to provide ground vibration source of the reflected wave research on the Korean Peninsula earth's crust structures research. For this study we've done blasting twice-500 ㎏/charge per delay, 1,000 ㎏/charge per delay, and the specifications of blasting are the following - dia.: 300 ㎜, boring-depth : 100m, besides, we used the explosives and electric detonators which have sufficient detonating velocity and very excellent safety, capacity of detonating, accurate delay time. We charged explosives into steel pipe with bulk type to avoid dead pressure by ground water. And then we tested about pipe airtight and blasting to certificate which has no problem by using on this study. In the results, we succeeded each blasting in Seosan, Youngdong. For the Peak Sum Vector(PSV) around the blasting at the main points, its real measured PSV is higher 180 % than estimated PSV with USBM. In this study we can't to be analysis of vibration velocity, but to be key providing vibration source.

• Journal of the Korean Geophysical Society
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• v.10 no.1
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• pp.13-25
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• 2007

We investigated the undulation of Moho depth and the crustal structure of the continental margin in the East Sea along the Korea Peninsula from inversion and modelling using potential data and previous seismic results. Free-air gravity anomalies generally reflect topography effect. Bouguer gravity anomalies increase toward the Ulleung Basin, indicating that Moho depth is shallower under the Ulleung Basin. Positive magnetic anomalies exist along the continental margin and decrease toward the Ulleung Basin. In analytic signal, the small anomaly in the Hupo Bank infers that the Hupo Bank is uplifted by igneous intrusion and the strong anomaly on the continental slope denotes existence of SDR(seaward dipping reflectors), which are in accordance with the location of SDR detected in previous seismic studies. The inversion result of Bouguer gravity anomaly and the 2-dimensional gravity modelling indicate that the undulation of Moho depth shallows from the continental shelf toward the Ulleung Basin. This is in good agreement with the Moho depth calculated by the previous seismic velocity model using ocean bottom seismometer(OBS). The 2-dimensional gravity modelling infers magmatic underplating zone under the lower continental crust on the continental margin of the East Sea, indicating the possible rifiting of the continental margin.

• Economic and Environmental Geology
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• v.47 no.2
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• pp.147-168
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• 2014

The soil geochemical exploration was carried out targeting around Tri Le area far from about 30 km with northwestern direction from Que Phong within Nghe An province. The interval of sampling are horizontal 200 m interval with 23 line and longitudinal 300 m with 10 line, resulting in 228 soil samples. Based on the result of the soil geochemical exploration, the detailed pitting survey was carried out targeting the grid point with high TREO content, resulting in 75 soil samples within 7 pits. The geology of survey area are consisted of Ban Chieng biotite granite complex and granitic gneiss intruding Ban Khang formation comprising of quartz schist and marble. Main mineralization in the study area have the characteristics of occurrence with tin, ruby and REE-bearing monazite and xenotime to be thought as occurring at the alteration zone of granite complex. In order to elucidate the source rock of monazite and xenotime confirmed from heavy sand, soil geochemical exploration was carried out. As a analysis result with ICP-MS on the soil samples from the soil geochemical exploration, total REE oxide content of background amount to about 2 times of crustal abundance, enriching the heavy rare earth(about 2 times) and light rare earth(about 1.5 times). As a analysis result with ICP-MS on the soil samples from the soil detailed pit survey, we only identified outcrop considering as economic weathered granite body at the grid point 1-10 pit among 7 pits. As a synthetic consideration on the soil geochemical exploration and detailed pit survey, we tentatively designated Tri Le area as no promising target for REE. In 2014, we have the plan to carry out the soil geochemical exploration targeting the extended economic REE ore body in Quy Chau as project area from 2011 to 2012.

• 한국해양학회지
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• v.26 no.1
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• pp.1-12
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• 1991

A multi-disciplinary geophysical study including gravity, magnetic, and seismic reflection profiling was carried out in the area between the Clarion fracture zone and the Clippertone fracture zone o the northeastern equatorial Pacific basin. There are small free-air gravity anomalies of less than 20 mgal over seamounts and the east-west trending abyssal hills. The negative residual gravity anomalies over seamounts may indicate the existence of low density seamount roots compared to surrounding oceanic crust. Non-existence of magnetic lineations and the magnetic anomalies of small smplitude with no polarity change in the east-west direction support that the study area belongs to the Cretaceous magnetic quite zone. Positive magnetic anomalies over seamounts offset 100 km in the east-west direction in the southern part of the study area suggest a possibility of left-lateral movement of those seamounts along unknown fractures. The sedimentary section in the study area can be divided into three units (Unit I, unit IIA, and Unit IIB) n the basis of reflection characteristics. the total thickness of sedimentary section varies from 200 to 400 meters and the sedimentary section is thicker in the southern area of rough topography near the seamount belt than in the northern flat area. Manganese nodules are abundant in the southern part of the study area where the ridges are developed and the Unit I layer is thicker than 100 meters.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.41-48
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• 2009

Natural magnetic fields are attenuated by electrically conductive water. For that reason, marine magnetotelluric surveys have collected data at long periods (1000-100 000 s). The mantle structure has been the main target of seafloor magnetotelluric measurements. To ascertain crustal structure, however, electromagnetic data at shorter periods are important, e.g. in investigations of megathrust earthquake zones, or in natural resource surveys. To investigate of the former, for example, electromagnetic data for periods of less than 1000 s are necessary. Because no suitable ocean bottom electromagnetometer (OBEM) has been available, we have developed a small OBEM and ocean bottom electrometer (OBE) system with a high sample rate, which has an arm-folding mechanism to facilitate assembly and recovering operations. For magnetic observation, we used a fluxgate sensor. Field observations were undertaken to evaluate the field performance of our instruments. All instruments were recovered and their electromagnetic data were obtained. Results of the first experiment show that our system functioned well throughout operations and observations. Results of other field experiments off Tottori support the claim that the electromagnetic data obtained using the new OBEM and OBE system are of sufficient quality for the survey target. These results suggest that this device removes all instrumental obstacles to measurement of electromagnetic fields on the seafloor.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.12-17
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• 2017

We construct 3D SV-wave velocity structure of the crust and the upper mantle beneath East Asia from Rayleighwave group-velocity measurements. For the construction of the SV-wave velocity model at 10 ~ 100 km depth, we used seismic data recorded at 321 broadband stations in Korea, Japan, and China. Rayleigh-wave group-velocity dispersion curves were obtained by using the multiple filtering technique in the period range from 3 to 150 s. High SV-velocity anomalies are imaged beneath the East Sea from 10 km depth to deeper depth, implying that the Moho beneath the East Sea is between at 10 ~ 20 km depth. We estimated the Moho beneath the Korean peninsula to be around 35 km based on the depth where a high-velocity anomaly is observed. The SV-wave velocity model shows prominent fast S-velocity anomalies near northeastern Japan, associated with the subducting Pacific plate. Low-velocity anomalies are found beneath the east coast of the Korean peninsula at 100 km depth, which may play a role in the formation of the Ulleungdo and the Ulleung basin. We observed low-velocity anomalies beneath the Yamato basin at 100 km depth as well, which may indicate the upwelling of fluid from the Pacific plate via dehydration at deeper depth.